Project description:Calorie restriction (CR) is a dietary intervention that extends lifespan and healthspan in a variety of organisms. CR improves mitochondrial energy production, fuel oxidation and reactive oxygen species scavenging in skeletal muscle and other tissues, and these processes are thought to be critical to the benefits of CR. PGC-1a is a transcriptional coactivator that regulates mitochondrial function and is induced by CR. Consequently, many of the mitochondrial and metabolic benefits of CR are attributed to increased PGC-1a activity. To test this model for the first time, we examined the metabolic and mitochondrial response to CR in mice lacking skeletal muscle PGC-1a (MKO). Surprisingly, MKO mice demonstrated a normal improvement in glucose homeostasis in response to CR, indicating that skeletal muscle PGC-1a is dispensable for the whole-body benefits of CR. In contrast, gene expression profiling and electron microscopy demonstrated that PGC-1a is required for the full CR-induced increases in mitochondrial gene expression and mitochondrial density in skeletal muscle. These results demonstrate that PGC-1a is a major regulator of the mitochondrial response to CR in skeletal muscle, but surprisingly show that neither PGC-1a nor mitochondrial biogenesis in skeletal muscle are required for the metabolic benefits of CR. Control (FLOX) and PGC-1a skeletal muscle specific knock out (MKO) mice were placed on a control diet [C] or a calorie restriction diet [CR] for 12 weeks. RNA was isolated from TA/EDL muscles for microarray analysis. The following numbers of mice were analyzed from each group: C FLOX: n = 6; C MKO: n = 7; CR FLOX: n = 6; CR MKO: n = 7. Mice were mixed C57/BL6 and 129 background.
Project description:Calorie restriction (CR) is a dietary intervention that extends lifespan and healthspan in a variety of organisms. CR improves mitochondrial energy production, fuel oxidation and reactive oxygen species scavenging in skeletal muscle and other tissues, and these processes are thought to be critical to the benefits of CR. PGC-1a is a transcriptional coactivator that regulates mitochondrial function and is induced by CR. Consequently, many of the mitochondrial and metabolic benefits of CR are attributed to increased PGC-1a activity. To test this model for the first time, we examined the metabolic and mitochondrial response to CR in mice lacking skeletal muscle PGC-1a (MKO). Surprisingly, MKO mice demonstrated a normal improvement in glucose homeostasis in response to CR, indicating that skeletal muscle PGC-1a is dispensable for the whole-body benefits of CR. In contrast, gene expression profiling and electron microscopy demonstrated that PGC-1a is required for the full CR-induced increases in mitochondrial gene expression and mitochondrial density in skeletal muscle. These results demonstrate that PGC-1a is a major regulator of the mitochondrial response to CR in skeletal muscle, but surprisingly show that neither PGC-1a nor mitochondrial biogenesis in skeletal muscle are required for the metabolic benefits of CR.
Project description:Resveratrol is a naturally occurring compound that profoundly affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here we treated 10 healthy, obese men with placebo and 150 mg/day resveratrol in a randomized double-blind cross-over study for 30 days. Resveratrol supplementation significantly reduced sleeping- and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1alpha protein levels, increased citrate synthase activity, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels, and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30 days of resveratrol supplementation induces profound metabolic changes in obese subjects, mimicking the effects of calorie restriction. double-blind randomized cross-over study, Expression profiling by microarray
Project description:In utero undernutrition is associated with obesity and insulin resistance, although its effect on skeletal muscle remains poorly defined. We report that, in mice, adult offspring from undernourished dams have decreased energy expenditure, decreased skeletal muscle mitochondrial content, and altered energetics in isolated mitochondria and permeabilized muscle fibers. Strikingly, when these mice are put on a 40% calorie restricted diet they lose half as much weight as calorie restricted controls. Our results reveal for the first time that in utero undernutrition alters metabolic physiology having a profound effect on skeletal muscle energetics and response to calorie restriction in adulthood. We have used a mouse model of low birth weight generated through 50% food restriction of mouse dams during the third week of gestation. We have studied in utero food restricted offspring and control offspring that were not food restricted in utero in both the ad libitum and calorie restricted states. Gene expression profiling was performed on tibialis anterior muscle from 8 mice per group, pooled in pairs.
Project description:In utero undernutrition is associated with obesity and insulin resistance, although its effect on skeletal muscle remains poorly defined. We report that, in mice, adult offspring from undernourished dams have decreased energy expenditure, decreased skeletal muscle mitochondrial content, and altered energetics in isolated mitochondria and permeabilized muscle fibers. Strikingly, when these mice are put on a 40% calorie restricted diet they lose half as much weight as calorie restricted controls. Our results reveal for the first time that in utero undernutrition alters metabolic physiology having a profound effect on skeletal muscle energetics and response to calorie restriction in adulthood.
Project description:Resveratrol is a naturally occurring compound that profoundly affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here we treated 10 healthy, obese men with placebo and 150 mg/day resveratrol in a randomized double-blind cross-over study for 30 days. Resveratrol supplementation significantly reduced sleeping- and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1alpha protein levels, increased citrate synthase activity, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels, and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30 days of resveratrol supplementation induces profound metabolic changes in obese subjects, mimicking the effects of calorie restriction.
Project description:This experiment was conducted to identify target genes of the microRNA-499 in skeletal muscle of transgenic mice that overexpressed miR-499. The following abstract from the submitted manuscript describes the major findings of this work. Coupling of mitochondrial function and skeletal muscle fiber type by a miR-499/Fnip1/AMPK circuit. Jing Liu, Xijun Liang, Danxia Zhou, Ling Lai, Tingting Fu, Yan Kong, Qian Zhou, Rick B. Vega, Min-Sheng Zhu, Daniel P. Kelly, Xiang Gao, and Zhenji Gan. Upon adaption of skeletal muscle to physiological and pathophysiological stimuli, muscle fiber type and mitochondrial function are coordinately regulated. Recent studies have identified pathways involved in control of contractile proteins of oxidative type fibers. However, the mechanism for coupling of mitochondrial function to muscle contractile machinery during fiber type transition remains unknown. Here, we show that the expression of the genes encoding type I myosins, Myh7/Myh7b and their intronic miR-208b/miR-499 parallels mitochondrial function during fiber type transitions. Using in vivo approaches in mice, we found that miR-499 drives a PGC-1a-dependent mitochondrial oxidative metabolism program to match shifts in slow-twitch muscle fiber composition. Mechanistically, miR-499 directly targets Fnip1, a known AMP-activated protein kinase (AMPK)-interacting protein that negatively regulates AMPK, a known activator of PGC-1a. Inhibition of Fnip1 reactivated AMPK/PGC-1a signaling and mitochondrial function in myocytes. Restoration of the expression of miR-499 in the mdx mouse model of Duchenne muscular dystrophy (DMD) reduced the severity of DMD. Thus, we have identified a miR-499/Fnip1/AMPK circuit that can serve as a mechanism to couple muscle fiber type and mitochondrial function. Keywords: muscle, contractile fiber type, mitochondrial function, microRNA, gene regulation RNA from three wild-type (non-transgenic (NTG)) and three miR-499 overexpressing (MCK-miR-499) mice was analyzed. three replicates of each are provided.
Project description:Resveratrol has been reported to improve metabolic function in metabolically-abnormal rodents and humans, but has not been studied in non-obese people with normal glucose tolerance. We conducted a randomized, double-blind, placebo-controlled trial to evaluate the metabolic effects of 12 weeks of resveratrol supplementation (75 mg/day) in non-obese, postmenopausal women with normal glucose tolerance. Although resveratrol supplementation was well-tolerated and increased plasma resveratrol concentration without adverse effects, it did not change body composition, resting metabolic rate, plasma lipids, or inflammatory markers. A two-stage hyperinsulinemic-euglycemic clamp procedure, in conjunction with stable isotopically-labeled tracer infusions, demonstrated that resveratrol did not increase liver, skeletal muscle, or adipose tissue insulin sensitivity. Consistent with the absence of in vivo metabolic effects, resveratrol did not affect its putative molecular targets, including AMPK, Sirt1, Nampt, and Pgc-1α, in either skeletal muscle or adipose tissue. These findings demonstrate that resveratrol supplementation does not have metabolic effects in non-obese women. We compared gene expression profile in subcutaneous abdominal adipose tissue and skeletal muscle (vastus lateralis) biopsy samples obtained from non-obese people before and after 1) placebo (PLC), 2) resveratrol (RES), and 3) calorie restriction (CR) intervention.
Project description:Endurance and resistance exercise training induce specific and profound changes in the skeletal muscle transcriptome. PGC-1a; coactivators are not only among the genes differentially induced by distinct training methods, but also participate in the ensuing signaling cascades that allow skeletal muscle to adapt to each type of exercise. While endurance training preferentially induces PGC-1a1 expression, resistance exercise activates the expression of PGC-1a2, a3, and a4. These three alternative PGC-1a isoforms lack the arginine-serine (RS) and RNA Recognition Motifs (RRM) characteristic of PGC-1a1. Discrete functions for PGC-1a1 and a4 have been described, but the biological role of PGC-1a2 and a3 remains elusive. Here we show that different PGC-1a variants can affect target gene splicing through diverse mechanisms, including alternative promoter usage. By analyzing the exon structure of the target transcripts for each PGC-1a isoform, we were able to identify a large number of previously unknown PGC-1a2 and a3 target genes and pathways in skeletal muscle. In particular, PGC-1a2 seems to mediate a decrease in the levels of cholesterol synthesis genes. Our results suggest that the conservation of the N-terminal activation and repression domains (and not the RS/RRM) is what determines the gene programs and splicing options modulated by each PGC-1a isoform. By using skeletal muscle-specific transgenics for PGC-1a1 and a4, we could validate in vivo splicing events observed in in vitro studies. These results show that alternative PGC-1a variants can affect target gene expression both quantitatively and qualitatively, and identify novel biological pathways under the control of this system of coactivators.